Fix crashes on ExDoc

[erszcz]

This partially addresses #78. Fixing the initial IO.ANSI.format() issue uncovers more crashes which also have to be taken care of.

[erszcz]

With #79 and josefs/Gradualizer#415 the current error is:

17:23:58.147 [error] Unsupported guards format [{:op, [generated: true, location: 327], :"=:=", {:var, 327, :_arity@1}, {:var, [generated: true, location: 327], :_@4}}, {:op, [generated: true, location: 327], :"=:=", {:var, 327, :_name@1}, {:var, [generated: true, location: 327], :_@3}}]
** (FunctionClauseError) no function clause matching in :lists.map/2

    The following arguments were given to :lists.map/2:

        # 1
        #Function<61.46472160/1 in :typechecker.infer_clause/2>

        # 2
        {:op, [generated: true, location: 327], :"=:=", {:var, 327, :_arity@1}, {:var, [generated: true, location: 327], :_@4}}

    (stdlib 3.15.2) lists.erl:1242: :lists.map/2
    (stdlib 3.15.2) lists.erl:1243: :lists.map/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:3368: :typechecker.infer_clause/2
    (stdlib 3.15.2) lists.erl:1243: :lists.map/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:3354: :typechecker.infer_clauses/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:1868: :typechecker.type_check_fun/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:1490: :typechecker.type_check_expr/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:2258: :typechecker.do_type_check_expr_in/3

[erszcz]

With this Gradualizer diff:

diff --git a/src/typechecker.erl b/src/typechecker.erl
index 204e146..c574d2b 100644
--- a/src/typechecker.erl
+++ b/src/typechecker.erl
@@ -3365,7 +3365,9 @@ infer_clause(Env, {clause, _, Args, Guards, Block}) ->
     % TODO: Can there be variable bindings in a guard? Right now we just
     % discard them.
     % TODO: Should we check that guards return boolean()?
+    is_list(Guards) orelse io:format("Guards is not a list!\nEnv: ~p\n", [EnvNew]),
     lists:map(fun (GuardConj) ->
+                      is_list(GuardConj) orelse io:format("GuardConj is not a list!\nEnv: ~p\n", [EnvNew]),
                       lists:map(fun (Guard) ->
                                         type_check_expr(EnvNew, Guard)
                                 end, GuardConj)

We get this log (truncated):

18:04:49.911 [error] Unsupported guards format ...
GuardConj is not a list!
Env: {env,
         ...
         #{module => 'Elixir.ExDoc.Language.Elixir',records => #{},
           types => #{}},
         false,false,true,
         [{clauses_controls,true}],
         30,
         {type,0,any,[]}}
** (FunctionClauseError) no function clause matching in :lists.map/2

    The following arguments were given to :lists.map/2:

        # 1
        #Function<61.83922501/1 in :typechecker.infer_clause/2>

        # 2
        {:op, [generated: true, location: 327], :"=:=", {:var, 327, :_arity@1}, {:var, [generated: true, location: 327], :_@4}}

    (stdlib 3.15.2) lists.erl:1242: :lists.map/2
    (stdlib 3.15.2) lists.erl:1243: :lists.map/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:3369: :typechecker.infer_clause/2
    (stdlib 3.15.2) lists.erl:1243: :lists.map/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:3354: :typechecker.infer_clauses/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:1868: :typechecker.type_check_fun/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:1490: :typechecker.type_check_expr/2
    (gradualizer 0.1.3+build.1082.refa72e7f0) /Users/erszcz/work/erszcz/gradualizer/src/typechecker.erl:2258: :typechecker.do_type_check_expr_in/3

Which leads to location 327 - the line with the pinning operators below:

  defp find_function_line(module_data, {name, arity}) do
    Enum.find_value(module_data.private.abst_code, fn
      {:function, anno, ^name, ^arity, _} -> anno_line(anno)
      _ -> nil
    end)
  end

It seems the pinning operator compiles down to guards which are a problem for both Gradient (https://github.com/esl/gradient/blob/main/lib/gradient/ast_specifier.ex#L543-L553) and Gradualizer (https://github.com/josefs/Gradualizer/blob/master/src/typechecker.erl#L3371 - GuardConj is not a list).

[erszcz]

It seems to me we miss logic to handle non-unary guard lists in https://github.com/esl/gradient/blob/main/lib/gradient/ast_specifier.ex#L543-L553. Let's consider the following example:

3> merl:quote("fun (A, B) when A =:= 1; B =:= 2, B =/= 3 -> ok end").
{'fun',1,
       {clauses,[{clause,1,
                         [{var,1,'A'},{var,1,'B'}],
                         [[{op,1,'=:=',{var,1,'A'},{integer,1,1}}],
                          [{op,1,'=:=',{var,1,'B'},{integer,1,2}},
                           {op,1,'=/=',{var,1,'B'},{integer,1,3}}]],
                         [{atom,1,ok}]}]}}

The alternative has two conjunctions (A =:= 1 and B =:= 2, B =/= 3). The first conjunction has only a single condition (A =:= 1), but the second conjunction has two conditions (B =:= 2 and B =/= 3).

[erszcz]

This patch fixes the crash, but it doesn't pass the guards through mapper yet:

diff --git a/lib/gradient/ast_specifier.ex b/lib/gradient/ast_specifier.ex
index fea2a43..9a5c226 100644
--- a/lib/gradient/ast_specifier.ex
+++ b/lib/gradient/ast_specifier.ex
@@ -548,7 +548,7 @@ defmodule Gradient.AstSpecifier do
 
       gs, {ags, ts} ->
         Logger.error("Unsupported guards format #{inspect(gs)}")
-        {gs ++ ags, ts}
+        {[gs | ags], ts}
     end)
   end

[erszcz]

This doesn't crash on ExDoc anymore. It reports some errors, though not a lot. I've not revised them yet, so some reported errors might be false positives, but at the very least we do not crash anymore.

[Premwoik]

Looks good :)